X-ray apparatus



Dmn 17,'1946. WWA'TSN 2,412,662

l x-RAY'APPARATUS Filed Aug. 23.11944 Patented Dec. 17, 1946 X-RAYAPPARATUS William Watson, Ilford, England Application August 23, 1944,Serial No. 550,733 In Great Britain September 3, 1943 (Cl. Z50-105) 11Claims. 1

This invention relates to apparatus for defining the cross-sectionalarea of a beam of radiation which may be visible light, infra-red, ultraviolet,

'X-rays or gamma rays, or other radiation. The

a short distance between the X-ray tube and the fluorescent screen. Bykeeping the distance short the electrical power energising the iii-raytube may be kept to a minimum and this is desirable where theobservation of the uorescent image on the screen takes some time, as inthe observation of movement in medical radiology. On the other hand foroptimum conditi-ons for radiography it is usually desirable to adjustthe apparatus so that there is a relatively long distance between theX-ray tube and the fluorescent screen since this increases the sharpnessof the image.

The cross-sectional area of the beam of X-r'ays employed is normallydened by inserting a diaphragm of adjustable aperture in the path of therays. It will be appreciated therefore, that the actual size of theimage on the fluorescent screen will vary with the distance of thescreen from the X-ray tube, assuming a constant size of aperture in axed position relative to the X-ray tube, and it is frequently the casethat on increasing the distance between the fluorescent screen and theX-ray tube to that most suitable for radiography, the size of the imageon the screen becomes too great and has to be reduced by manuallyadjusting the aperture to a smaller area.

According to the present invention in apparatus comprising asubstantially point shaped source of rays, a substantially plane elementon which a beam of said rays is desired to fall, and aldiaphragmsubstantially parallel to said plane element and located between saidelement and said source of rays, the aperture in said diaphragm servingto denne the cross-sectional area of a beam of said rays emitted by saidsource, there is provided a longitudinally extensible member extendingbetween and joining the said source and the said plane element, the saidextensible member having one or more points in its length which move asthe said member is extended or retracted a distance which is a constantfraction of the amount by which the said member is eX- mounted on thesaid extensible member at one of such points.

More particularly, according to this invention, the source of rays is anX-ray tube and the plane element is a fluorescent screen or photographicplate, ilm or paper.

In one form of the invention the extensible member consists of asymmetrical system of crossed levers of the type known as a lazy-tongs.The pivotal points along the centre line of such a system, where thelevers cross one another, and also the other points where the levers arepivotally connected, are points within the meaning defined above. Bysecuring one end of the lazytongs to the X-ray tube and the other to thefluorescent screen and by mounting the diaphragm on one of the saidpivotal points an increase or decrease in the tube-screen distance,effected by extending or retracting the lazy-tongs, causes aproportional movement of the diaphragm. Thus the cross sectional area ofthe beam of X-rays falling on the screen remains constant irrespectiveof the tube-screen distance.

The lazy-tongs system may be of the type in which the levers cross oneanother at the midpoints of their length, but they may be arranged tocross at some other point along their length, the system necessarilybeing symmetrical along its longitudinal axis.

In another form of the invention the extensible member consists of auniform spring. This may be in the form of a coiled metal spring or maybe a length of elastic material such as rubber cord. It is the propertyof a uniform spring that all points along its length move, when thespring is extended or retracted, a distance which is a constant fractionof the distance by which the spring is extended or retracted. Thediaphragm may, therefore, be mounted at any convenient point along thelength of the spring. By securing one end of the spring to the X-raytube and the other end to the fluorescent screen and by mounting thediaphragm at some convenient point along the length of the spring, it isensured that the cross-sectional area of beam of X-rays falling on thescreen is constant irrespective of the tube-screen distance.

It will be apparent that any other form of extensible member satisfyingthe conditions stated above may be similarly employed.

It is sometimes considered desirable to employ a plurality of diaphragmsof successively increasing aperture from X-ray tube to screen since itis considered that this reduces penumbral shadow.

It is to be understood that several such dia.-

;tensied., 0r retreated the said. .diaphragm @eine Y t phragm-s may beused in the present invention 3 by mounting them at successive pivotalpoints on the lazy-tongs linkage or by mounting them at intervals alongthe length of a spring linkage as described above.

As indicated above it is essential that the diaphragm be arranged so asto be substantially parallel to the iiuorescent screen or other element.However, the axis of the X-ray beam need not lbe normal to thefluorescent screen nor need the aperture in the diaphragm be centrallydisposed in relation to the axis of the beam; an eccentric aperture willgive an image of constant size and position on the screen when mountedin accordance with this invention.

It will be appreciated that the actual construction of the device musttake into account the Weight of the parts involved; the X-ray tube,diaphragm and screen or any of them may conveniently be mounted inguides cr runners to take their weight, the extensible member servingonly to control their relative positions.

The aperture in the diaphragm is preferably adjustable `but once setwill, as indicated above, give the same size image for any tube-screendistance.

The invention will now be described with reference to the accompanyingdiagrammatic drawing in which Figures 1 and 2 show one form ci theapparatus, employing a lazy-tongs `connection, in different degrees ofextension. Figures 3 and 4 show 'an alternative form of the apparatus,employing a spring connection, in different degrees of extension.Figures 5 and 6 show a form of apparatus similar to that of Figures 1and 2, employing an ec'centrically apertured diaphragm, in diiierentdegrees of extension. Fig- 'ures 7 and 8 show a form of apparatussimilar to that of Figures l and 2 where the screen is not normal to theX-ray source, in different degrees of extension. Figs. 9 and 10 show twomodications of the apparatus 'shown in Fig. 1.

Referring to Figure 1, there is provided a source of X-rays H and aIscreen l2. Thefscreen l2 is linked through a lazy-tongs 'connection I3to the source of X-ra'ys so that 'one mid-point end Id of the lazy-tongssystem is located at the screen i2, and the other mid-point end 'is isconnected to a point on the X-ray tube (not shown) correspondin'g withthe source ofthe X-'rays i l. At another mid-point i6 of the lazy tongssystem is located 'a diaphragm Il having an aperture I8. The path of theX-rays from the source H to the screen |2 is shown bythe limiting linesIQ.

In Figure 2 the apparatus of Figure 1 is shown in extended form. It willbe noted that, although no change has been made in the `dimensions 'ofthe aperture I8, the limiting lines i9 meet the screen l2 in the sameposition as in Figure l. In other words, the screen land the source ofX-rays 'il have been moved further apart without any change in thedimensions oi the area of the screen l2 reached by the X-rays.

Figure 3 illustrates similar apparatus in which there is employed aspring 2i) instead of the lazytongs system I3. One end of the spring`lil is anchored at the screen i?. and the other end l5 at the source ofX-rays ii'. The diaphragm il is located at a point along the length ofthe spring. In Figure l this system is shown extended, and it will beseen that asin thevcase of Figures l and 2, the area of vthe screenreached by the X-rays is not affected by increasing the distance betweenthe screen and the source of IEC-rays. A

Figure 5 illustrates apparatus of the type of 'X-rays, and the diaphragmIl is mounted at the same angle. This apparatus is shown extended inFigure 8, and it will be seen that, although the yscreen I2 anddiaphragm Il are at an angle to the normal, the same conditions hold asin the other examples.

Fig. 9 illustrates an apparatus of the type shown in Fig. l wherein aplurality of diaphragms il, 2i] and 2i are arranged substantiallyparallel to screen i2 and located between this screen and the X-ray tubei5. These diaphragms Il, 29 and 2l are provided with apertures |18, 22and 23, respectively, adjusted so as to define the cross sectional area'of the beam of X-rays emitted by the X-ray tube I l. Of course, inaccordance with the present invention, these diaphragms are each mountedat a point where the levers are pivotally connected, namely diaphragmil' at point l 5, diaphragm 2l? at point 2d and diaphragm 2l at point25.

Fig. 10 illustrates an apparatus of the type shown in Fig. 1 wherein thelevers i3 cross at some other points than the midpoints of theirlengths. Of course, in order to obtain proper operation of such asystem, it is necessary that the same -is symmetrical along itslongitudinal axis.

Although in the drawing the element l2 has been designated as a screen,it will be clear that it may alternatively be a photographic iilm,plate, paper or other substantially plane element on which the X-raybea-m is intended to fall. If desired, other diaphragms of appropriatesize may be located at Aother mid-points or any other piv. otal point ofthe lazy-tongs systems of Figures 1, 2, 5, 6, '7 and 8 or `at other'points alo-ng the length of the spring 29 in Figures -3 and 4 for thepurpose, for example, 'of reducing penumbra] shadow. Only one diaphragmhas been shownin the drawing for the sake of simplicity.

Whilst the foregoing description relatesV particularly to the case wherethe source of rays is an X-ray tube, it is to be clearly understood thatit may, instead, be a substantiallyr point source of other radiation, e.g. visible'li'ght, infrared,-ultra-violet or Jgamma rays. Similarly thenucrescent screen 'or photographic element may be replaced by any otherplane surface.-

What I claim is: Y

1. Apparatus comprising a substantially point shaped sourcevof rays, asubstantiallyplane ele'- ment on which a beam of said rays is desiredYto fall, a diaphragm substantially parallel Vto said plane element andlocated between said element and said source of rays, the aperture in'said diaphragm serving to dene the-cross-sectionafl area of a 4beam ofsaid rays emittedby said source, and a longitudinally extensiblfememberextendingbetween said `source and said plane element and joining thesame, the said extensible member having at least one poi-nt in 'itslength which moves -as vthe said member is extended `or re tracted adistance which is a constant fraction or the amount by which the'sa-iolmember Vis eX- tended or retracted, vthe said diaphragm being 5 mountedon the said extensible member at one such point.

2. X-ray apparatus comprising a substantially point shaped source ofX-rays, a substantially plane element on which a beam of X-rays fromsaid source is desired to fall, a diaphragm substantially parallel tosaid plane element and located between said element and said X-raysource, the aperture in said diaphragm serving to define thecross-sectional area of a beam of X-rays emitted by said source, and alongitudinally extensible member extending between said source and saidplane element and joining the same, the said extensible member having atleast one point in its length which moves as the said member is extendedor retracted a distance which is a constant fraction of the amount bywhich the said member is extended or retracted, the said diaphragm beingmounted on the said extensible member at one such point.

3. X-ray apparatus comprising a substantially point shaped source ofX-rays, a substantially plane element on which a beam of X-rays fromsaid X-ray source is desired to fall, a diaphragm substantially parallelto said plane element and located between said element and said X-raysource, the aperture in said diaphragm serving to define thecross-sectional area of a beam of X-rays emitted by said X-ray source,and a crossed lever lazy-tongs connection extending between said X-raysource and said plane element and joining the same, the Said diaphragmbeing mounted at a point on such connection where the levers arepivotally connected.

4. X-ray apparatus comprising a substantially point shaped source ofX-rays, a substantially plane element on which a beam of X-rays fromsaid X-ray source is desired to fall, a diaphragm substantially parallelto said plane element and located between said element and said X-raysource, the aperture in said diaphragm serving to dene thecross-sectional area of a beam of X-rays emitted by said X-ray source,and a crossed lever lazy-tongs connection extending between said X-raysource and said plane element and joining the same, the said diaphragmbeing mounted at a point on such connection where the levers cross oneanother.

5. X-ray apparatus comprising a substantially point shaped X-ray source,a substantially plane element on which a beam of X-rays from said X-raysource is desired to fall, a diaphragm substantially parallel to saidplane element and 10- cated between said element and said X-ray source,the aperture in said diaphragm serving to define the cross-sectionalarea of a beam oi X-rays emitted by said X-ray source, and a uniformspring extending between and connecting said X-ray source and said planeelement, the said diaphargm being mounted at a point along the length ofsaid spring.

6. X-ray apparatus comprising a substantially point shaped X-ray source,a substantially plane X-ray sensitive element on which a beam of X-raysfrom said X-ray source is desired to fall, a diaphragm substantiallyparallel to said plane X-ray sensitive element and located between saidX-ray sensitive element and said X-ray source, the aperture in saiddiaphragm serving to define the cross-sectional area of a beam of X-raysemitted by said X-ray source, and a crossed lever lazy-tongs extendingbetween and connecting said X-ray source and said plane X-ray sensitiveelement, the said diaphragm being mounted at a point on such connectionwhere the levers are pivotally connected.

7. X-ray apparatus comprising a substantially point shaped X-ray source,a substantially plane X-ray sensitive element on which a beam of X-raysfrom said X-ray source is desired to fall, a diaphragm substantiallyparallel to said plane X-ray sensitive element and located between saidX-ray sensitive element and said X-ray source. the aperture in saiddiaphragm serving to dene the cross-sectional area of a beam of X-raysemitted by said X-ray source, and a crossed lever lazy-tongs extendingbetween and connecting said X-ray source and said plane-X-ray sensitiveelement, the said diaphragm being mounted at a point on such connectionwhere the levers cross one another.

8. X-ray apparatus comprising a substantially point shaped X-ray source,a substantially plane X-ray sensitive element on which a beam of X-raysfrom said X-ray source is desired to fall, a diaphragm substantiallyparallel to Said plane X-ray sensitive element and located between saidX-ray sensitive element and said X-ray source, the aperture in saiddiaphragm serving to dei-lne the cross-sectional area of a beam ofX-rays emitted by said X-ray source, and a uniform spring extendingbetween and connecting said X-ray source and said plane X-ray sensitiveele ment, the Said diaphragm being mounted at a point along the lengthof said spring.

9. X-ray apparatus comprising a substantially point shaped X-ray source,a substantially plane element on which a beam of X-rays from said X-raysource is desired to fall, a plurality of diaphragms substantiallyparallel to said plane element and located between said element and saidX-ray source, the apertures in said diaphragms being adjusted to definethe cross-sectional area of a beam of Xv-rays emitted by Said X-raysource, and a crossed lever lazy-tongs connection extending between saidX-ray source and said plane element and joining the same, the saiddiaphragms each being mounted at a point on such connection where thelevers are pivotally connected.

10. X-ray apparatus comprising a substantially point shaped X-raysource, a substantially plane element on which a beam of X-rays fromsaid X-ray source is desired to fall, a plurality of diaphragmssubstantially parallel to said plane element and located between saidelement and said X-ray source, the apertures in said diaphragms beingadjusted to define the cross-sectional area of a beam of X-rays emittedby said X-ray source, and a crossed lever lazy-tongs connectionextending between and joining said X-ray source and said plane element,the said diaphragms each being mounted at a point on such connectionwhere the levers cross one another.

11. X-ray apparatus comprising a substantially point shaped X-raysource, a substantially plane element on which a beam of X-rays fromsaid X-ray source is desired to fall, a plurality of diaphragmssubstantially parallel to said plane element and located between saidelement and said X-ray source, the apertures in said diaphragms beingadjusted to define the cross-sectional area of a beam of X-rays emittedby said X-ray source, and a uniform spring extending between andconnecting said X-ray source and said plane element, the said diaphragmsbeing mounted at different points along the length of said spring.

WILLIAM WATSON.

